Composite materials are increasingly used as substitutes for conventional materials, such as aluminum and steel alloys, in various structural components due to the generally high strength-to-weight ratio inherent in composite materials. For instance, composite parts are presently used as parts for aircrafts. Composite materials generally include a network of reinforcing fibers that are applied in layers, and a polymeric resin that substantially wets the reinforcing fibers to form an intimate contact between the resin and the reinforcing fibers. High speed composite layup machines can be used to form each layer. These machines can lay composite material at a rate of up to 3000 inches per minute.
Problems can arise, however, when foreign object debris or contamination is on or within the formed composite part prior to curing. For example, small amounts of entrapped or surface-adhering moisture or other types of contamination can result in delamination and porosity of the composite material once the curing is completed. In addition, debris such as small pieces of bagging materials, Teflon tapes, or breathing material used during the composite layup can become entrapped within a composite layer, resulting in delamination, porosity, and/or wrinkles in the composite part. Some foreign object debris materials are transparent or blend well with a surface color of the composite material, making detection of the foreign object debris materials using visible light cameras difficult or impossible.
If foreign object debris materials are not detected and removed prior to curing, inconsistencies resulting from the foreign object debris material can cause an entire part to be rejected. The rejection of such parts can be quite costly, and can also cause scheduling delays and inventory problems.